Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
1998-09-17
2001-03-06
Cain, Edward J. (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
Reexamination Certificate
active
06197850
ABSTRACT:
FIELD OF THE INVENTION
This invention refers to ferrules and other feeding head and supply elements for casting molds, suitable for manufacturing metallic parts, to a procedure for their obtention, and also to suitable formulations for the production of the same.
BACKGROUND OF THE INVENTION
As is known, the obtention of metallic parts by means of molding, comprises the pouring of cast metal into a mold, the solidification of the metal through cooling and the demolding or extraction of the formed part, by means of the removal or destruction of the mold.
Said molds may be metallic or may be formed by aggregates of different materials (ceramics, graphites and especially, sand), normally hardened by the action of agglomerates. Generally, the sand molds are obtained by filling a molding die with sand.
Said molds shall be equipped with gates or orifices for the communication between the internal and the external cavity, through which the cast metal in molding or casting form, is poured. Likewise, due to the shrinkage of the metal during the cooling, the mold shall be provided with vertical cavities or flash channels which are filled with reserve cast metal with the object of forming a feeding head intented to compensate the shrinkage or drawing of the metal.
The purpose of the feeding head is to supply the part when the medium is shrunk in the same, due to which the metal shall be kept in the feeding head in liquid condition a longer time than the part. For this reason, the flash channels are normally covered with ferrules manufactured with isothermic or even exothermic refractory materials (insulations) which delay the cooling of the metal contained in the feeding heads in order to ensure its fluidity when the drawing in the cast metal is produced.
The gates through which the cast metal is poured are also constructed from refractory, insulating and even exothermic materials, with similar composition to that of the ferrules.
Suitable insulation refractory compositions are known for the production of ferrules and other feeding head and supply elements for casting molds, with insulating properties, constructed from a refractory material in the manner of particles, organica and/or inorganic fibers and agglomerantes.
Sutiable exothermic refractory compositions are also known for the production of ferrules and other heeding head and supply elements for casting molds, with exothermic properties, comprised of a refractory filler material in the form of fibers or particles, agglomerants and, optionally, selected loads from among an easily oxidizable metal and an oxidant agent, capable of oxidizing said metal. Additionally, in order to improve the sensitivity of the exothermic refractory composotion, an inorganic fluorine flux is generally included. British Patentes Nos. GB 627678, 774491, 889484 and 939541 disclose exothermic refractory compositions which contain inorganic fluorides.
Additionally, the PCT application, published with International Publication Number WO94/23865, discloses a composition for a casting mold of metals which comprises hollow micro beads containing alumina, in which the alumina content is at least, 40% in weight.
The great majority of the ferrules which are consumed at world level are manufactured by vacuum and wet molding, followed by drying and polymerization of the resins at high temperature, such as is mentioned in Spanish Patent N° ES-8403346. A standard procedure of this type comprises the stages of:
the suspension in water of a mixture formed by the materials used in the manufacturing of the ferrule, for example, aluminosilicate fibers, aluminum, iron oxide and phenolic resins, or alternatively, a mixture formed by siliceous sands, aluminum scoria, cellulose, aluminum and phenolic resins;
the aspiration of said aqueous suspension by means of vacuum through an exterior and interior mold; and
the demolding of a green or wet ferrule, deposited on a tray, which in turn is introduced into an oven in which it remains between 2 and 4 hours at a temperature of approximately 200° C., and finally, left to cool.
On occasions, all the aluminosilicate stock material is not found in the form of fibers since a part of the same may have been replaced by hollow micro beads of said aluminosilicate material with the object of decreasing the necessary quantity of product and reducing the cost of the final product. Such micro beads are then used as loading element.
This procedure permits the obtention of insulating or exothermic ferrules, but it presents numerous disdadvantages, among which the following are to be found:
the impossibility of obtaining ferrules with the sufficient external dimensional exactitude, since the aspiration of the mixture through the mold produces a good exactness of the ferrule on the internal face (the one which is in contact with the mold) but not of the other face. This inexactitude makes the external contour of the ferrules not coincide dimensionally with the internal cavity of the flash channels, often originating important difficulties for its placement and attachment. Even when there is a double mold, it is difficult to keep to the measurements due to its subsequent handling in green condition. In this sense, techniques have been developed for the placement of the ferrules in their housing, such as is disclosed in German Patent N° DE P 29 23 393.0;
it requires long production times;
it presents difficulties in the homogeneization of the mixtures;
it impossibilitates the introduction of rapid changes in the formulation;
it presents certain hazards during the manufacturing process and polution of residual waters; and
the materials used in the form of fibers may cause alergical pathologies, such as itching, and skin and mucous irritation, to the operators.
Another procedure for the manufacturing of ferrules consists in mixing sand, exothermic materials and a specific type of resin, for example, mixing sodium silicate and alkaline or novolac phenolic resins, and subsequently, performing a manual or blow molding of the obtained mixtures. With said procedure, parts of great dimensional exactitude may be obtained, both internal and external, with exothermic properties, though never with insulating properties. Though this procedure is simpler that the wet means, its employment presents serious limitations since, on one hand, it is not possible to obtain ferrules with insulating characteristics and, on the other hand, the ferrules obtained are extraodinarily hygroscopic.
Finally, Application WO94/23865 discloses a blowable composition based on aluminium silicate hollow micro beads, though requiring that the alumina content of the same be over 40
a
, which makes unusable a significant part of said by product, because a very important part of the aluminium silicate hollow micro beads generated as industrial by product, have a lower richness than the 40% weight in alumina.
As may be appreciated, a procedure exists for the manufacturing of ferrules by wet means and vacuum molding which provides ferrules equipped with insulating or exothermic properties, though with dimensional inexactitude, the development of which presents numerous disadvantages, and on the other hand, there exists a simpler production procedure of ferrules by dry means and manual or blow molding, though only permitting the obtention of ferrules provided with exothermic properties, not insulation, but with dimensional exactness.
It would be very desirable to have ferrules and other feeding head and supply elements provided with insulating or exothermic properties, which would present dimensional exactness, and which, additionally, could be manufactured by means of a simple procedure which would overcome the previously indicated disadvantages as regards the known procedures. The invention provides a solution to said problems which comprises the use of a refractory material, such as aluminium silicate, in the form of hollow micro beads with an alumina content below 38% in weight, in the formulation of a suitable composition for the production of said ferrules and feeding head and supply elem
Diaz Maruri Francisco Jose
Fernandez Tomas Posada
Gerenabarrena Rafael Sampedro
Iglesias Hernandez Luis
Lasa Urteaga Jose Joaquin
Cain Edward J.
Kemen Recupac S.A.
Notaro & Michalos P.C.
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